MI images in color

I've finally figured out a way to get color images from MI images. If enough people are interested, I can write up a tutorial on it. It would be for Photoshop 7.0, as that's the program I use. So, anyone wanna hear it?

YES!!!

YES!!!

You betchya! In fact, um3k, I sure would also like to know how to get colour photos from the Pan Cam filter photos.

Thanks in advance!

Ok, well, color from the pancam photos is the easier one, so I'll start with that. To get color images from the pancam using photoshop, you must first obtain 3 images of the same view, all taken through different filters. The preferred filters are L4, L5 and L6. L4 is red, L5 is green, and L6 is blue. When L4 is not available, you can use L2 and L3, this will simply result in less accurate colors. Similarly, when L6 is not available, you can use L7. In photoshop, create a new image, dimensions 1024x1024, color mode RGB. Copy and paste the L4, L5 and L6 images into the Red, Green, and Blue channels, respectively.

For color MI images, you need to use an image taken through the M1 filter for the red channel, and the corresponding M2 image for the green and blue channels. You then will probably need to align the R channel with the G and B channels. First, align the channels as closely as possible. Then, if the channels have a size difference, enlarge the smaller channel (or channels) to match the larger channels (or channel). Usually it is only necessary to enlarge by as little as 100.1 percent. Once the channels are aligned, go to Image > Adjustments > Channel Mixer. The settings I usually use are:
Red Channel:
150% R
0% G
-50% B
Green Channel:
0% R
100% G
0% B
Blue Channel:
-100% R
0% G
200% B
You may adjust the settings for better contrast, of course. As I said before, this tutorial was written for Photoshop 7.0, but most decent photo- and image-editing software will have similar functions. Hopefully I haven't been too confusing.
Here's a few sample images created with this method, which have been reduced to 50% their original size and combined into a single image:

cool beans!

I will try to find some Earth sample MIs taken with/without filter to give you a calibration. Of course, NASA didn't photograph any color charts this way...

or DID they? ( he says menacingly)

I recall seeing color marks on the border of the sundial for calibration. I'm pretty sure I saw color photos of these at the beginning of the mission, or pictures taken before launch. You'll just have to look around.

Er, I don't think there has ever been any MI image of the sundial. Hey, I wonder if the arm would allow that?

I don't think you'll be able to find any images for calibration, but you could compare the colors of the MI images to the colors of their pancam counterparts. I've found that although the MI images do not produce true color, they give an accurate representation of the contrast between, say, blue rocks and orange dust.

I vaguely remember an article by Land a long, long time ago about 2 filter color photography...

I will try to find it.

Yes, here ir is...

Well, for color astrophotography, exposures are often only made through red and blue filters. These are used for their respective channels, and the green channel is an average of the two. This process, of course, would not produce accurate results on earth, as there is much more variation between the three channels (due mainly to the abundance of rather colorful life).

Wow, that is quite odd indeed.

From

The dust cover window is made of Kapton polyimide film, which has an orange tint. Color information can be obtained by taking images of a target with the cover closed and open. During preflight camera testing, a similar film was used to take images of various rock targets. An example of the type of color image products that we will generate using such data is shown in Figure 7. In this example, the MI images were enhanced and therefore do not show true color. However, the images taken with and without the dust cover show color variations that are also visible in the true color (scanned) image. We therefore expect that such basic color information will be helpful in interpreting MI images of rocks and soils on Mars. The spectral transmittance of the Kapton film that is used in the flight units was measured at NASA Johnson Space Center; the spectral response of the system (with the dust cover opened and closed) to rocks observed at the Mars Pathfinder landing site (Maki et al., 1999) is shown in Figure 8.

Figure 8 is the most interesting. Maybe NASA can create pseudo-real ( how's that for an oxymoron!) color images...

Maybe you can too...

That link again: http://europa.la.asu.edu/pgg/greeley/courses/pdf/pdf_gw/herkenhoff_2003.pdf

I can't believe how many times I have mistyped links today! Maybe it's because I've been awake since 3AM?

Hi

Well I'm quite surprised...I was expecting horrible results from this idea(use 2 channels only, and the third an average). I tried a few miscellaneous earth pics, eg

Original:

and UM3k's method (but adapted to PWP3.6)
(obtain R, B channels and create G=(R+B)/2

As far as "accuracy" for colours is concerned... I'm not a believer in the concept anyway. And at this time of night (-er- 5:35 am over here in my corner of the world) I'm not going to get too involved in any discussion on that!

So anyhow, I'm happy.

Now I just have to try H's link again... maybe it'll work this time.

-----Martin M

Bugger!

Well, try [Link]

----Martin M(I need an emoticon for "hopefully THIS will work")

I forgot to add the connection time was VERY long for the link...

uhhh 25.3 MEGAbytes......

I like that picture, Martin.
I was referring more to images with a lot of, say, foliage. The picture you used happens to be quite well suited to this method.

About pseudo-real color images, NASA already has, they did it with the first blueberry MI, and this, in fact, is what inspired me to figure out how to do it myself. Scroll down a bit on this page to see it. The "stretched" version more closely resembles the image that would be produced by my method, as the raw images available to the public (i.e., us) have already been "stretched."

This is a bit off topic; I tried printing horton's link, and the stupid printer paper jammed just over half way through. Needless to say, I was quite pissed, so I took the stack of printed paper (and of course the piece that got stuck), and sacrificed it by fire to the electronic gods. Meaning, I lit it on fire and threw it in my outdoor fireplace. Ten or so minutes later, I look out there and the sacrifice had set afire everything else in the fireplace. This isn't all that big of a deal, of course, since I was planning on burning it anyways. It's just, I was waiting until night time to burn the rest.

Agni will reward your sacrifice with a boon -- er, which way were you facing when you sacrificed the printout? ( THIS IS IMPORTANT!)